A major feature of this year’s election cycle has been the focus on the super-wealthy individuals whose million dollar checks are funding the super PACs.

It’s not a new story that campaign contributions are incredibly concentrated and come from the very rich. As I documented in December, just 1% of 1% of Americans (actually 26,783 individuals) accounted for about one quarter of all political donations to candidates in 2010. All contributed at least $10,000.

But the question has always been: what do rich political donors get for their contributions?

One argument is that these individuals are buying special favors, including ambassadorships and other prime posts.

And while one can find occasional examples of the above, to my mind the more convincing claim has always been the more subtle one: that relying so heavily on rich donors leads candidates to be more sympathetic to the general concerns of their donors.

To raise money from a bunch of rich investors is to also take the time to listen to a bunch of rich investors and what they think about tax and financial policy. And to keep the campaign donations coming requires a certain policy sensitivity to what these donors think. It’s not so much a quid-pro-quo as it is a process of self-enlightened worldview osmosis.

The poor never have as much influence as the middle class, and the middle class never has as much influence as the affluent. Second, over the last four decades, responsiveness to the affluent has steadily increased while responsiveness to the middle class and the poor has depended entirely on the existence of the congenial circumstances just described.

He knows this because he looked at surveys of voters on a wide range of policies going back to 1964 on a range of policy issues and then looked at which policies passed. Here are the key figures, from his Monkey Cage posts:

What this shows that it doesn’t really matter what low-income or middle-income voters think about a policy. They might favor it. They might oppose it. It has no real effect on how likely the policy is to happen.

But among high-income individuals, there’s a clear pattern. If rich people are in favor, the policy is significantly more likely to become law. (The y-axis in both charts is logit regression coefficients. The coefficients translate into about a 65% increase in the probability of a policy passing when it goes from 0% to 100% support among rich people).

Gilens notes that on many issues, there’s not a whole lot of difference between what poor, rich, and middle-class people think. But on some issues there are some serious differences, particularly on tax, regulatory, and trade issues. Gilens writes:

Greater representational equality would have a substantial effect on several important economic policies. We would have a higher minimum wage, more generous unemployment benefits, stricter corporate regulation (on the oil and gas industries in particular), and a more progressive tax regime. Some of these policies are favored by a majority of Americans at the 90th income percentile as well, but not with sufficient enthusiasm to overcome opposition from business and other interests. We would also see a more protectionist trade strategy and less foreign aid.

Interestingly, Gilens notes that in presidential election years, policy becomes more responsive to poor and middle-class voters. But these programs are also more likely to lose funding later, when the poor and middle-class voters are less important to politicians because they don’t participate in the ongoing fundraising wars.

Along those lines, here’s another killer figure from Gilens:

Yes, rich people are more likely to vote, and more likely to volunteer on a political campaign. But where they really shine is in the giving of money.

There’s more to explore in the book and in Gilens’ posts.

And there are also some questions that go beyond his scope. As he notes, his data only looks at income by decile, and there are some interesting questions about whether the top 1% are even different from the top 10%. There is some evidence that indeed they do. They tend to care significantly more about deficits than the overall economy, and they tend to be very bullish on the private-sector and down on the government. None of this is surprising.

Gilens’ findings are an important part of the conversation about who is funding our campaigns and what they are getting. If we rely on the wealthiest Americans to finance our elections, is it any coincidence that our politicians are highly responsive to the policy preferences of rich people, while the preferences of poor and middle-class voters have pretty much no effect? Me thinks not.